ch 18 a&p 2

In an ECG recording, which of the following coincides with ventricular repolarization?

t wave

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.

isovolumetric contraction, ventricular ejection, isovolumetric relaxation Yes, the ventricles must contract and eject blood before they relax and fill again.

Which statement is correct regarding the intrinsic heart rate?

During parasympathetic stimulation, acetylcholine released by parasympathetic neurons opens chemically gated potassium channels in the plasma membrane

Which event does NOT happen during ventricular diastole?

Atrioventricular valves close because of the contracting ventricles. During ventricular diastole, the ventricles are relaxed. The ventricles have ejected a good portion of their blood into the elastic arteries, and the pressure in the ventricles is now lower than the pressure in the atria and the arteries. This causes the atrioventricular valves to open and the semilunar valves to close.

Which of the following statements is correct concerning the cardiac cycle?

In late ventricular diastole, all chambers are relaxed and filling to about seventy percent of their capacity. The completion of the cardiac cycle occurs when all the chambers of the heart are relaxed which occurs during late ventricular diastole.

Which of the following is correct about the filling of the ventricles?

Most blood flows passively into the ventricles through open AV valves. Yes, most of the ventricular filling is passive; atrial contraction adds just a little more blood.

In the non-exercising heart, which event of the cardiac cycle lasts the longest?

atrial diastole There has to be adequate time during the cardiac cycle to provide enough blood return to the heart for adequate cardiac output to the lungs and body systems. Remember the path of blood through the heart

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle Yes, backflow of blood in the aorta (towards the left ventricle) closes the aortic semilunar valve.

Cardiac muscle cells are __________.

mechanically, chemically, and electrically connected to one another

Which structure provides a rapid-conduction path that tenses the papillary muscles before the ventricular myocardium contracts, preventing "slamming" of the right AV cusps?

moderator band

Increased pressure in the ventricles would close what valve(s)?

AV valves only Yes, increased pressure in the ventricles would close the AV valves.

Which of the following statements most accurately defines what is happening during the second phase of ventricular systole of the cardiac cycle?

Blood is being ejected from the ventricles through open semilunar valves. The electrical stimulation conducted through the heart causes contraction of the ventricles. During the second phase of ventricular systole, the heart is far enough along in the cycle that the pressure generated by the contracting ventricles has opened the semilunar valves silently and pushed the blood out into the aorta and pulmonary trunk.

Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.

Pressure in the atria would be greater than the pressure in the ventricles. Yes, higher pressure in the atria than in the ventricles forces the AV valves to open and blood moves into the ventricles.

The portion of the tracing of an electrocardiogram, ECG, that represents ventricular depolarization is the __________.

QRS complex The QRS complex represents the entire events of ventricular depolarization.

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

ventricular diastole Yes, both occur during ventricular diastole when the ventricles are not actively contracting and ejecting blood.